This invention relates to forming metallic components, and more specifically to hot stretch forming and creep forming of titanium and its alloys.
Stretch forming is a well-known process used to form curved shapes in metallic components, by pre-stretching a workpiece to its yield point while forming it over a die. This process is often used to make large aluminum and aluminum-alloy components, and has low tooling costs and excellent repeatability.
Titanium or titanium alloys are substituted for aluminum in certain components, especially those for aerospace applications. Reasons for doing so include titanium's higher strength-to weight ratio, higher ultimate strength, and better metallurgical compatibility with composite materials.
However, there are difficulties in stretch-forming titanium at room temperature because their yield point is very close to their ultimate tensile strength with a minimal percent elongation value. Therefore, titanium components are typically bump formed and machined from large billets, an expensive and time-consuming process.
Accordingly, there is a need for an apparatus and method for stretch-forming titanium and its alloys.